1. Field of the Invention
The present invention relates to a system for desalination of a fluid containing charged species, and particularly to a three-electrode structure for capacitive deionization desalination.
2. Description of the Related Art
Capacitive deionization (CDI) involves the electrostatic- or applied potential-mediated attraction/repulsion of ions from water to oppositely charged electrode surfaces, thus depleting the ion concentration in liquids, such as water. Positive ions (or cations) like sodium (Na+) will be attracted to the negative electrode (cathode), and negative ions (or anions) like chlorine (Cl−) will be attracted to the positive electrode (anode).
Existing systems include methods for desalting water and dewatering of suspensions using a combination of attraction and repulsion of ions. These systems use only a 2-electrode systems connected to a DC power supply and ion exchange materials for selective adsorption and repulsion.
These conventional CDI cell designs assume that the potential applied is equally distributed between the two or more electrodes within the cell, thus enabling equal adsorption of both anions and cations from the water stream, i.e., if ‘X’ volts are applied across the electrodes, it will be divided into +‘X/n’ and −‘X/n’ volts, where ‘n’ is the number of electrodes in the CDI cell, thus forming alternate positive and negative electrodes, or a single positive and negative electrode in case of a two-electrode CDI cell.
Because the potential is not equally divided between two electrodes, there is an uneven flux of energy, and thereby leading to the removal of merely cations because of predominant positive potential.
Thus, a three-electrode structure for capacitive deionization desalination solving the aforementioned problems is desired.